1. Field of the Invention
The present invention relates to an image deformation device for deforming an input image by correcting the pixel position of each pixel in the input image.
2. Description of Related Art
In an image output device, such as a printer using an electrophotographic process, or the like, because an output image is deformed due to the fixing and/or the irregularity of the paper feeding, the deformation of the output image is suppressed by deforming the image data in a direction opposite to the deforming direction.
In case that an image deformation process is a simple correcting process, such as the enlargement (or the reduction) shown in FIG. 12, the rotation shown in FIG. 13 or the like, by inputting the parameter, such as the rotation angle, the magnification or the like, to the deformation processing unit, the deformation processing unit can calculate the positional shift amount of each pixel based on the parameter and deform the image.
However, because the actual deformation (distortion) of the output image, which is caused in an image output device, is complicated due to a plurality of factors, in order to correct the above deformation, a complicated deformation process shown in FIG. 14 is required. Therefore, it is not possible to completely eliminate the deformation of the output image by a simple correction, such as the rotation, the enlargement, the reduction or the like, which can be carried out by using the above calculation.
Accordingly, in order to eliminate the distortion based on the actual value of the distortion of the output image, the positional correction amount for each pixel (the shift amount in the vertical direction and the shift amount in the horizontal direction) is previously calculated and is stored in a memory. Then, by reading the positional correction amount for each pixel from the memory, the position of each pixel is corrected. As a result, various types of image deformation can be corrected and the positional correction can be carried out more precisely (See FIG. 15). However, in this case, because the positional correction amount for each pixel is held, an enormous memory for storing the positional correction amount is required.
In a general printer, there are some cases in which the number of pixels in one page is about 80 mega pixels when the resolution of the image is 600 dpi. When it is assumed that 16 bit data is held as the positional correction amount for one pixel having four colors, it is required that the memory has the capacity of 1 Gbits in order to hold the positional correction amounts for one page.
Because the image deformation process for cancelling the distortion of the output image is generally carried out in real time during the output of the image, the image deformation process is carried out by using the image processing LSI (Large Scale Integration) which can carry out the high speed processing. In case that the above positional correction amount data for each pixel is stored in the SRAM (Static Random Access Memory) of the image processing LSI, to which the correction unit of the image processing LSI refers, the necessary capacity of the SRAM is increased and the size of the image processing LSI is enlarged. As a result, the image deformation device becomes extremely expensive, or it is actually impossible to include the SRAM in the image processing LSI.
As a technology for reducing the data size of the positional correction amounts to be held in the image processing LSI, for example, the following image processing controller is disclosed in Japanese Patent Application Publication No. 2009-122763. In this image processing controller, the positional correction amount data for only the pixels arranged at intervals after the thinning out is held, and the positional correction amount for the thinned pixels is calculated based on the held data to deform the image to be displayed on the display unit.
In an image output device, such as a printer or the like, the resolution of the image is high as compared with a display unit, and the number of pixels is extremely large. Therefore, although the technology disclosed in Japanese Patent Application Publication No. 2009-122763 is applied, it is required to largely thin the data. As a result, the precision of the positional correction is significantly deteriorated.